As substrate processing apparatuses for performing a predetermined processing on a wafer as a substrate, a film forming apparatus that performs film formation processing by CVD (chemical vapor deposition) or PVD (physical vapor deposition) and an etching apparatus that performs etching processing are known. In recent years, the substrate processing apparatus has increased in size with the increase in the diameter of wafer and, therefore, the increase in the weight of the substrate processing apparatus has become an issue to be concerned about. Thus, a lightweight aluminum member has been widely used as a material of components of the substrate processing apparatuses.
Generally, since an aluminum member has a low corrosion resistance to a corrosion gas or a plasma that is used for specific processing in the substrate processing apparatus, an alumite film having a corrosion resistance is formed on the surfaces of components made of the aluminum members, for example, a cooling plate (see, for example, Japanese Patent Laid-open Application No. 2007-204831). Moreover, the formed alumite film has pores and is generally subjected to a sealing process for sealing the pores.
However, there have been cases in which a high power plasma processing, typically represented by HRAC (high aspect ratio contact) processing and the like, is performed on wafers. In the high power plasma processing, the temperature of a cooling plate rises, but a sealed alumite film generally has a low heat resistance. For this reason, in the plasma processing, damages such as cracks develop in the alumite film formed on the cooling plate, and the alumite film is partially peeled off to generate particles. To solve the above problems, the present inventor conceived an alumite film forming method, in which an alumite film is semi-sealed, whereby the heat resistance of the alumite film is improved (see, for example, Japanese Patent Laid-open Application No. 2008-81815).
Recently, much higher power plasma processing has been under consideration. Therefore, even though the alumite film is formed in accordance with the above-described alumite film forming method, the alumite film has an insufficient heat resistance, and the alumite film can be damaged, thereby generating particles.
Further, a cooling plate having the alumite film formed thereon requires a process for forming thereon a circuit for supplying radio frequency power. However, cutting oil or hydrocarbon-based cleaning fluid which is used in the processing infiltrates into the alumite film, so that the hydration sealing of the alumite film is promoted. If the hydration sealing is promoted, the heat resistance of the alumite film can be deteriorated, and thus the alumite film can be damaged to thereby generate particles.